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Delta Air Lines reported a hefty profit for Q3, but its earnings have started to decline on a year-over-year basis.

Summer is the peak season for airlines in North America. Traditionally, it's when airlines pull in their biggest quarterly profits of the year.

Not surprisingly, Delta Air Lines(NYSE:DAL) reported on Thursday morning that it earned a hefty profit last quarter. However, considering that it continued to benefit from falling fuel prices and steady (if not spectacular) economic growth, Delta's Q3 results were hardly inspiring.

Delta's earnings by the numbers

Delta's revenue fell 5.6% year over year last quarter to $10.48 billion, despite a modest increase in capacity. That included nearly 2 percentage points in negative impacts from Delta's August technology outage and lower yen hedging gains. Nearly every other important financial metric moved in the wrong direction, too.

Key Delta Air Lines Metrics: Q3 2016

Revenue

$10.48 billion

Adjusted pre-tax income

$1.91 billion

Adjusted EPS

$1.70

Passenger unit revenue

Down 6.8%

Adjusted non-fuel unit costs

Up 0.1%

Data source: Delta Air Lines Q3 earnings release.

Delta did a good job of holding non-fuel unit costs roughly flat last quarter. Furthermore, its adjusted fuel price fell to $1.48/gallon from $1.80/gallon a year earlier, providing hundreds of millions of dollars of savings.

However, this was not enough to offset Delta's 6.8% decline in passenger revenue per available seat mile (PRASM). As a result, pre-tax income declined by $278 million year over year. Despite a lower tax rate and a lower share count, Delta's adjusted earnings per share slipped to $1.70 from $1.74 a year earlier.

Furthermore, Delta's Q3 earnings performance would have been even worse had the company not settled all of its fuel hedging losses for 2016 during the previous quarter. That pulled forward $455 million of hedging losses into Q2, some of which would otherwise have been incurred last quarter.

That said, it's important to recognize that Delta's Q3 pre-tax margin of more than 18% should put it solidly in the upper half of the industry. It's only a disappointment relative to the company's stellar 2015 performance.

Revenue stays weak in Delta's biggest markets

Delta's year-over-year earnings decline was driven by a continuation of weak revenue trends across much of the globe. Like its peers, Delta reports revenue for four geographic regions: domestic, transatlantic, transpacific, and Latin America. Of those four regions, PRASM grew year over year in only one: Latin America.

Unfortunately, Latin America is the least important region for Delta, contributing a little over 6% of its revenue. Delta's 1.4% year-over-year PRASM growth there thus did little to offset its sharp PRASM declines of at least 7% in each of the other three geographic regions.

Looking ahead

For Q4, Delta expects PRASM to decline 3% to 5% year over year. As a result, management forecast a Q4 operating margin of 14% to 16%. That would translate to a pre-tax margin of approximately 13% to 15%, down slightly from 15.2% in Q4 2015.

One important caveat is that Delta's guidance does not incorporate any impact from the tentative agreement Delta recently reached with its pilots. Since the pilot deal provides an 18% pay raise retroactive to the beginning of 2016, it would push Delta's Q4 costs significantly higher if it is ratified, weighing on margins.

With Delta's profit margin starting to decline, management has become even more determined to get unit revenue growing again. Delta CEO Ed Bastian stated that the company will target capacity growth of just 1% in 2017. With year-over-year comparisons getting easier and credit card revenue expected to rise in 2017, Delta has a good chance of returning to unit revenue growth within the next few quarters.

Author

Adam Levine-Weinberg is a senior Industrials/Consumer Goods specialist with The Motley Fool. He is an avid stock-market watcher and a value investor at heart. He primarily covers airline, auto, retail, and tech stocks. Follow him on Twitter for the latest news and commentary on the airline industry! Follow @AdamLLW